1. Field of the Invention
The present invention relates to nucleotide sequences which encode enzymes involved in the formation of carbohydrates in plants and, more particularly to sequences which, after insertion into a plant genome, alter the carbohydrate concentration and composition in transformed plants and plant cells.
2. Description of the Related Art
Because of the continuous growth in the world population, there is a continuously growing demand for nutrients and raw materials. It is one of the goals of biotechnological research to achieve a modification in the content as well as in the yield of crops.
Of particular interest is the possibility of using plant ingredients as renewable sources of raw material sources, e.g. for the chemical industry. The use of plant ingredients as renewable sources of raw materials is of great importance for two reasons. First, mineral oil and coal deposits which are the main sources of raw materials for the petrochemical industry are finite. Therefore, alternative, renewable raw material sources must be developed.
Second, there is a surplus of crops grown for their nutritive properties in Europe and North America which has led to financial and political problems. The modification of plants to produce alternative products for which there is a higher quantitative demand could solve this problem.
Renewable raw materials can be divided into fats and oils, proteins and carbohydrates, such as mono-, di-, oligo- and polysaccharides. The most important polysaccharides are starch and cellulose. In the European Economic Community, the total starch production in 1987-1988 was obtained from maize (60%), wheat (19%) and potato (21%).
In order to increase the use of plant starch as an industrial raw material, the quantity of the starch must meet the demands of the processing industry. Important considerations include the ratio of amylose to amylopectin, the chain length of the starch, the branching grade of the amylopectin, and the size of the starch granules.
The main biochemical synthetic pathways for the production of starch in higher plants are well known. Starch consists of amylose and amylopectin. Amylose consists of a linear xcex1-1,3-glucan and amylopectin consists of xcex1-1,4-glucans, which are connected to each other by xcex1-1,6 linkages, and thus form a branched phytoglycogen. The so-called branching enzyme (Q-enzyme) is responsible for the introduction of the xcex1-1,6-linkage. One method for the production of starch which only has a linear xcex1-1,4-glucan structure is by the inhibition of the enzymatic activity of the proteins and/or the inhibition of the biosynthesis of the branching enzyme.
New biotechnology processes for the genetic alteration of dicotyledonous and monocotyledonous plants by transfer and stable installation of single isolated genes or groups of genes are known (Gasser and Fraley, Science 244, 1293-1299). The possibility of specific expression of foreign genes inserted in the plant by gene technology, primarily in potato tubers, is also known (EP 375092 and Rocha-Sosa et al., EMBO J. 8, 23-29 (1989)).
It is therefore an object of the present invention to provide nucleotide sequences which encode enzymes involved in the formation of carbohydrates in plants.
It is an additional object of the present invention to provide DNA sequences which can be used to alter the carbohydrate concentration and composition in transgenic cells and plants.
It is a further object of the present invention to provide plasmids, plant cells and plants containing the nucleotide sequences.
In the context of the invention, the term xe2x80x9cplantxe2x80x9d means a commercially useful plant, preferably maize, barley, wheat, rice, peas, soya beans, sugar cane, sugar beet, tomato, potato or tobacco. xe2x80x9cIsolatedxe2x80x9d means having a higher purity than exists in nature, but does not require purification from a natural source. Isolated nucleotides encoding a branching enzyme may be produced synthetically, or by isolating cDNA thereof from a cDNA library or by any of the numerous other methods well understood in the art.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.